I. Technical Field
The present invention relates to a power transmission device which is convenient if used for connection and disconnection in power transmission between, for example, an automobile engine and an air conditioner.
II. Related Art and Other Considerations
Conventionally, as a power transmission device of this type, there is a device in which an electromagnetic clutch is provided between a pulley and a rotating shaft that drives a compressor. The electromagnetic clutch is on while an engine is rotating so that a rotational power is transmitted to the rotating shaft from the pulley. On the other hand, the electromagnetic clutch is turned off when the engine is stopped to disconnect the rotating shaft from the pulley so that the rotating shaft is driven to rotate by a motor (see JP 2001-140757 A).
However, the conventional power transmission device requires the electromagnetic clutch and a control part that controls on-off action of the electromagnetic clutch. This makes the structure of the power transmission device complicated and increases the device size.